Do you kick their butts every time?

Instructors often have the mind set that they need to always teach a "kick butt" class in order to have a good following of students. If "kick butt" means hard hills, break aways and sprints in every class, then that instructor may be doing a disservice to the clients, not to mention to him/herself. If we apply the FITT Principle, which comes out of years of research into the effects of exercise on the human body, then we will understand that working into the anaerobic zones at every training does not promote fitness. It is considered overtraining. Overtraining has negative results which list includes but is not limited to: sleep deprivation, weight gain or loss, irritability, increased rate of injury and a lower immune system.
The human body is amazing in that it can get used to numerous forms of abuse. The need to survive is so strong in the human body, that it will learn to function in the worst of conditions, just as it will thrive in ideal conditions (proper food/water, enough rest, stress control and appropriate exercise). I find it pretty easy to identify instructor who are teaching kick butt classes all the time. They often have horse voices from all the yelling, they seem wired like they are always drinking too much coffee, they often are detached and don't look at their students when they teach, they ignore newcomers and don't know how to cue to their level, they go into class wanting their Spinning® fix, they get sick a lot, they get injured a lot, and clients and co-workers will shake their heads at the mention of the instructor's name and make comments like, "He's the crazy one. Don't take his class unless you want to crawl out."
there are guidelines that all instructors should have memorized and should be utilizing when training. The FITT Principle, created by doctors, physiologists and trainers at the highest levels of education, stands for frequency, intensity, time and type of exercise. Frequency for cardiorespiratory training is 3-5x per week, intensity is 64-94% of maximum heart rate (updated in ACSM's 8th addition of Guidelines for Exercise Testing and Prescription, 2010), time is 10-90 minutes (also updated in 2010) and type includes cycling, walking, jogging, running, swimming, or aerobic based group exercise classes like step.
When one exercises more intensely, by going running or practicing sprinting on a bike, then the amount of time and the frequency should be limited to the lower end of the recommendations. When one exercises less intensely, such as walking, or working in the seated flat in Spinning®, then the amount of time and frequency may increase to the top of the recommendations.
Instructors must consider all of these elements when teaching classes and should educate their students to the guidelines. Anaerobic training should only be done once or twice per week, even on superfit athletes due to the amount of recovery necessary to gain benefit from the training. Learn to pad the anaerobic sessions with aerobic sessions the day before and the day after, so the body enters the high end training rested and the session afterwards promotes recovery of those systems (heart, lungs, fast twitch muscle fibers, tendons and ligaments). Behaving differently causes inflammation in the body which leads to a long list of unfortunate chronic problems down the line.
The education of your clients is simple. If I am going to offer sprint work, or anaerobic intervals in a class, I tell people that if they did sprints, or had a very hard workout the previous day, to avoid them today. I also tell people that they should strive for two really hard workouts per week and make the rest of them more moderate to really gain the benefits of their training without causing undue stress in the body. Consider how you have been teaching and how you may integrate these guidelines created by doctors, physiologists and trainers in order to create the ideal fitness level possible, with the least amount of negative side effects.
Written by master instructor Sabrina Fairchild for community.spinning.com blog on 3/26/2011